The National Electric Code (NEC) first specified Arc-Fault Circuit Interrupters (AFCIs) be used to protect branch circuits that supply receptacles installed in bedrooms in 1999. Currently, the 2011 NEC requires combination-type AFCI protection of branch circuits supplying outlets (including hard-wired devices like fans and lights) in most rooms in a house, including living areas, closets, hallways, and more (NEC 210.12). In most cases, AFCI protection will be provided by installing AFCI circuit breakers instead of normal circuit breakers in the home’s breaker box. Some exceptions allow AFCI protection at the outlet instead of the panel.
AFCIs are intended to trip, or disconnect electricity to the attached wiring, if arc current travels, or sparks, from the hot lead of the circuit to the ground or neutral lines. Combination-type AFCI’s add protection against sparks between the ends of a single broken conductor, and has been required since the 2005 NEC. The determination of whether current flow is due to normal usage of the circuit versus an arc fault is done by signal processing equipment within the AFCI.
